1. Technical Field
The present invention relates generally to glucans. More particularly, the invention relates to methods for extracting .beta.-glucans from cereal sources.
2. Background of the Invention
Glucans are structural polysaccharides present in the cell wall of yeasts, fungi and cereals. For example, (1.fwdarw.3)-,(1.fwdarw.4)- and mixed (1.fwdarw.3), (1.fwdarw.4)-.beta.-D-glucans are found in the endosperm cell wall of such cereals as barley and oat, among others. .beta.-Glucans affect the viscosity and hence the effectiveness of products derived from these sources. For example, the presence of .beta.-glucans in animal feed products is often undesirable. 0n the positive side, .beta.-glucans appear to influence digestion, assist in glucoregulation and lower serum cholesterol. Cereal .beta.-glucans are useful nutritional agents and have also been used as bulking agents in place of sucrose. Accordingly, efficient methods for removing unwanted .beta.-glucans from cereal sources, as well as purifying them for future use and study, are needed.
.beta.-Glucans have been extracted from oat flour and bran using a sodium carbonate solution and purified for analytical and nutritional purposes. Wood et al. Cereal Chem. (1978) 55:1038-1049; Welch et al. Nutr. Rep. Int. (1988) 38:551-561; Wood et al. Cereal Chem. (1989) 66:97-103. Wood et al. Cereal Chem. (1991) 68:31-39; and Wood et al. Cereal Chem. (1991) 68:530-536, describe the molecular characterization of oat .beta.-glucans. Knuckles et al. Cereal Chem. (1992) 69:198-202, describe the extraction of .beta.-glucan from barley and oats using dry milling and sieving. Such techniques offer advantages over wet extraction where solvent disposal may be a problem. However, dry milling and sieving techniques result in the presence of considerable starch and other components which may interfere with certain .beta.-glucan applications.